1. Field of the Invention
The present invention relates to a composition for forming a layer to be plated, a method of producing a metal pattern material, and a metal pattern material.
2. Description of the Related Art
Conventionally, a metal wiring board having a wiring formed from a metal pattern on a substrate made of an insulating material has been widely used in electronic devices or semiconductor devices.
Such a metal pattern material is produced typically by a subtractive method. This method includes forming, on a metal film formed on a substrate, a photosensitive layer that is sensitized by irradiating with actinic light, exposing the photosensitive layer with light in an imagewise manner, developing the same to form a resist image, forming a metal pattern by etching the metal film, and then peeling off the resist image.
In the subtractive method, the surface of the substrate is roughened so that the metal film can be tightly adhered thereto by means of an anchoring effect. Therefore, there has been a problem in that degradation in high-frequency characteristics may occur when the metal pattern material is used for metal wiring. Further, there has been a problem in that since the surface of the substrate needs to be treated with a strong acid such as chromium acid for roughening, a complicated process is required in order to obtain a metal pattern that exhibits excellent adhesiveness between the metal film and the substrate.
In order to solve the above problem, Advanced Materials (2000) Vol. 20, pp. 1481-1494 proposes a method of improving the adhesiveness between the substrate and the metal film without performing surface roughening, the method including subjecting the substrate surface to a plasma treatment and introducing a polymerization initiating group thereto, and then generating a graft polymer having a polar group on the surface of the substrate by polymerizing a monomer from the polymerization initiating group.
Further, International Publication No. WO08/050715 discloses a method of obtaining a metal pattern (plating film) that exhibits excellent adhesiveness with respect to a substrate, the method including forming a polymer layer on the substrate by generating a graft polymer that bonds to the substrate, performing plating with respect to the polymer layer, and then etching the obtained plating film.
However, the above method utilizes, as a compound that forms a graft polymer, a polymer having a polymerizable group and a non-dissociative functional group that interacts with a plating catalyst or a precursor thereof. Since this polymer has low affinity to an aqueous solution, highly alkali water needs to be used for developing a portion of the polymer layer formed on the substrate, thereby taking a long time for the development process.
The present invention has been made in view of the aforementioned circumstances, and aims to provide a composition that forms a layer to be plated, which layer can be developed with an aqueous solution and has an excellent adsorption property with respect to a plating catalyst or a precursor thereof. Further, the present invention aims to provide a method of producing a metal pattern material in which a metal pattern having excellent adhesiveness with respect to a substrate can be readily formed by performing development with an aqueous solution.